1. Field of the Invention
The invention relates generally to radio frequency actuation systems and, more specifically, to a secured ignition system for a motor vehicle.
2. Description of the Prior Art
In a conventional motor vehicle, the internal combustion engine of the vehicle is "started" by an electrical starter motor. Current to start the electrical starter motor, in turn, is supplied by a battery power source wherein the battery power source and the starter motor comprise part of the ignition system circuit of the motor vehicle.
The starter motor is contained in a housing located beneath the internal combustion engine of the motor vehicle and contains a rotatable armature. Translation of the rotatable armature causes contact with a flywheel which is connected in-line with the crankshaft of the internal combustion engine. When current is supplied to the starter motor, the armature is translated and rotated. This movement causes the flywheel to rotate, and, the crankshaft to rotate, thereby causing the internal combustion engine to "start".
Typically, a key-operated switch located on the steering column of the vehicle is connected in a series connection in the ignition system circuit containing the battery power source and the starter motor. Closing of the switch closes the ignition system circuit, allowing the starter motor to "start" the internal combustion engine. Security of the ignition system circuit is dependent upon the integrity of the key-operated switch. By shorting the key-operated switch, the ignition system circuit may be closed without the need of a key to close the switch. This is known as "hot wiring" starting.
Shorting the key-operated ignition switch is frequently the method used to "start" the internal combustion engine during theft of a motor vehicle. The switch is typically located on the steering column of the vehicle which is surrounded by a circular metal housing. By breaking open the metal housing, the switch may thereafter be quickly and easily shorted. Alternatively, the key switch may be broken by the forceful insertion of an object such as a screwdriver into the keyhole whereby the screwdriver thereafter effectively acts as a key to close the switch.
Several means have been developed which attempt to improve the integrity of the ignition system circuit to make theft of the vehicle more difficult. An encoding/decoding system is disclosed in U.S. Pat. No. 4,141,332 which prevents the starting of the engine merely by shorting the ignition key switch. An encoder housed in a secure housing located proximate to the ignition key switch is actuated by the turning of the key and the encoder then transmits a digital code through an electrical connection to a decoder located in the engine compartment. Only when the digital code received by the decoder agrees with a code stored in a memory component of the decoder is the starter allowed to start the motor. While this system provides a means of preventing theft of a vehicle by merely shorting the ignition key switch, the system suffers from a major disadvantage. The encoder and decoder must be installed as a set. If either the encoder or decoder fails, both must be replaced. The encoder is typically located on the housing of the drive shaft, or in the dashboard, and is not easily accessible. Replacement of the encoder/decoder is therefore a major undertaking.
It is therefore an object of the invention to provide a system to improve the security of a conventional unsecured ignition system.
It is a further object of the present invention to provide a security system which is both inexpensive and easily maintained.